I work at Aptivate - http://www.aptivate.org/ and while technically we're still a not-for-profit company with two directors nominally in charge, for a number of years we've been effectively running as a worker's co-operative with decisions made by consensus. You can read a fuller description of our internal processes at http://aptivate.org/en/about/how-we-do-things/ under "Management and Governance".